Lung Cancer is the leading cause of cancer death in the United States. Over the last decade, a significant paradigm shift has occurred in the understanding that lung cancer is a complex, heterogeneous, and multigene disorder with subsets containing specific genetic alternations that are critical to growth and survival of these cancers. Molecular subsets of lung adenocarcinoma, in particular, have been well characterized with respect to clinically relevant driver mutations, and it is now estimated that over half of NSCLC tumors with adenocarcinoma histology demonstrate such an oncogenic driver mutation or fusion, such as activating mutations in EGFR, fusion genes involving ALK, and rearrangements in ROS-1. In parallel, remarkable progress in therapeutics has brought a number of new drugs that target signaling pathways activated by above genetic alterations. These drugs include the tyrosine kinase inhibitors (tkis) such as erlotinib (targets EGFR mutation) and Crizotinib (targets ALK rearrangement). These therapies now offer unprecedented options to a subset of patients, often inducing dramatic responses and a prolonged progression free survival. However, many of these cancers invariably develop resistance to TKI therapy. The resistance is often mediated by a secondary mutation in the target gene or alternative pathways that supervene and bypass the original signaling pathway. Traditionally, tissue biopsies are used for molecular characterization of tumor, both at initial diagnosis and at the time of recurrence. However, multiple biopsies are not only expensive but also painful and may not always be feasible (e.g. deep seated lung lesions). The concept of blood biopsy/liquid biopsy is garnering momentum not only due to a non-invasive nature, but also due to the feasibility of frequent monitoring of patients to track response and resistance. Circulating tumor cells (CTCs) shed from primary tumor carry the key molecular signatures and could act as ideal surrogates for tissue biopsies. Recent advances in isolation technologies combined with the next generation tools for molecular analysis have shifted the paradigm in favor of liquid biopsy. Our laboratory has been working on developing microfluidic technologies that can isolate CTCs with high sensitivity and specificity. We have developed a new, highly sensitive technology to effectively isolate CTCs, incorporating a nanomaterial graphene oxide (GO). The nanomaterial, GO enhances the surface area many fold. Self-assembly of GO creates islands of nano-arms for sensitive CTC capture without the aid of three-dimensional structures. We have demonstrated the isolation of cells with high sensitivity even at low frequency of target cells (73% 32.4 at 3-5 cells/mL blood). Additionally, the gentler process preserves the viability of the cells, enabling an organotypic model for in-situ expansion of CTCs. We have recently published a novel radial fluid flow approach to isolate cells at 10mL/hr, increasing the throughput considerably without sacrificing specificity. In the proposed studies we propose to optimize GO Chip for high throughput (10mL/hr) capture using the radial flow principle and in situ 3D co-culture model for ex vivo expansion of CTCs. Furthermore, we will test the ability of our platform to predict response or resistance to targeted therapies using expanded CTCs. In summary, our proposed work will provide a non-invasive method for identifying primary and secondary mutations and allow ex-vivo drug testing to direct therapy specific to the patient. If successful, we would have a platform that involves non-invasive testing for driver mutations, resistance mutations as well as one that can be used for ex-vivo drug testing.